This video shows a system that estimates the pose of a flexible endoscopic instrument, based on the endoscopic images. A three-dimensional rendering of the instrument is matched to the actual instrument that is observed through the endoscopic camera. This system was evaluated in an anatomical model of a colon. The estimated position of the tip of the instrument was compared to measurements performed with an electromagnetic tracker. The errors of the position estimation were 2 mm, 2.2 mm and 1.7 mm in the horizontal (x), vertical (y) and away-from-camera (z) directions, respectively.